Field of the Invention
The invention relates to a brushless electric motor of a motor vehicle as well as a method for operating a brushless electric motor of a motor vehicle. The brushless electric motor can be part of an ancillary unit of the motor vehicle, such as a drive train actuator. The invention furthermore relates to a drive train actuator of a motor vehicle.
Description of the Background Art
In at least partially automated transmissions of a motor vehicle, the individual gears are set with the aid of a drive train actuator. The drive train actuator has a so-called shift finger and an electric motor, the shift finger being adjustable by the electric motor, and the position of the shift finger determining the desired gear ratio. A brushless electric motor, whose stator is energized with the aid of an electronic system, is usually used as the electric motor. The electronic system includes a number of semiconductor components, which are connected in a bridge circuit. The bridge circuit is conventionally a three-phase bridge circuit, and the stator has three field windings, which are connected to each other in either a delta or a star circuit with the aid of an interconnecting ring. To shield and avoid possible damage to the field windings, each of which includes a number of electric coils, the stator is disposed in a stator housing.
The semiconductor elements are activated as a function of an electric current flowing over the semiconductor components, provided that a field-oriented regulation is used. To monitor the power of the electric motor and to identify a possible fault, it is also necessary for the electric current flow to be detected by the electric coils. For example, a magnetic field is detected for this purpose, which surrounds the conductors carrying the electric current. A more cost-effective variant is to use a so-called shunt. An ohmic resistor is connected in series to the electric coil, and the electric voltage falling over the resistor is detected. The electric current is ascertained based on the ohmic resistance, on the basis of the known resistance value and the detected electric voltage. The disadvantage here is that another component, namely the shunt, must be introduced into the current path, which results in an increased complexity during manufacturing. Additional components are also required, which increases the manufacturing costs.